Fabrication and Characterization of NanoStructured Hydroxyapatite (HA)/ Yttria Stabilized Zirconia (YSZ) Composite Coatings by Sol – Gel Method

Hydroxyapatite (HA) is a major inorganic component consisting of human hard tissues, such as bones and teeth [1].Artificial HA, suffers from its intrinsic low mechanical properties, and thus cannot sustain heavy load or severe impact. One way to solve these problems is to apply HA coatings onto biocompatible metal substrates so as to achieve the necessary mechanical strength and bioactive properties at the same time [2]. The erratic bond strength between HA and stainless steel has raised concern over the long-term reliability of the implant. To overcome this problem, some attempts have been made. One of these approaches is the application of composite coatings. Zirconia (ZrO2), especially for yttria stabilized zirconia (YSZ), having the attributes of high strength and stress-incused phase transformation toughening, has been used to reinforce the hydroxyapatite coatings and to improve the bond strength of the HA coatings [2]. Y2O3 addition in to zirconia can stabilize the tetragonal phase plays a major role in the fracture toughness increase [2]. A mixture of chemistry co-precipitated HA and YSZ nanoparticles has not been reported so far. In this study Yttria- Stabilized Zirconia was used to form YSZ/HA composite coatings on surgical grade 316L stainless steel was carried out using sol–gel dip coating and calcination process